The creation of gene expression profiles or the analysis of the transcriptome has, with the establishment of microarray technology, taken hold to become an important tool in biomedical science.
Particularly the development of second-generation RNA sequencing methods (next-generation sequencing, NGS) has not only resulted in a drastic lowering of the costs for carrying out a transcriptome analysis, but has also increased the accuracy in identifying hitherto unknown gene activities. Examples of application areas of gene expression profiles are the diagnosis and prognosis of diseases, the aftercare analysis of therapies, the analysis of genetic predispositions, the investigation of pharmacological mechanisms of action and also the qualitative and quantitative investigation of growth and differentiation processes of cells and tissues.
A customary method of evaluating gene expression data is differential analysis, by means of which both the expression of known genes is investigated and the detection of unknown genes can be carried out. In that method, the expression data of the sample to be investigated are aligned or compared with the gene expression pattern of reference samples or else with the expression data of selected genes. For example, when investigating the expression of pathophysiologically relevant genes, the expression data of healthy tissue (reference sample) are compared with the expression data of diseased tissue (measurement sample) such as tumor tissue, for example. On the basis of this comparison, information can be provided in relation to the qualitative (yes/no answer) or the quantitative expression (increase or decrease in expression) of selected genes and this in turn can be assigned to a particular state, for example, a pathological state.
DE 10 2010 033 565 A1 discloses various markers for the in vitro determination of the pharmaceutical identity, purity or potency of chondrocytes (cartilage cells), by which the chondrocytes can be tested for their suitability for an expectedly successful chondrocyte transplantation. The establishment of said markers was borne by the fact that chondrocytes can vary greatly with respect to their suitability for use as autologous cells for an implantation for cartilage regeneration, specifically not only chondrocytes from one donor in relation to chondrocytes from another donor, but also chondrocytes from the same donor. Furthermore, it was taken into account that the culturing of chondrocytes can alter their properties such that they are no longer as suitable for an implantation as directly after isolation from the donor.
Although a selective analysis of a few genes, especially those involved in cellular metabolism, can definitely lead to powerful results in the quality assurance of cells to be transplanted, the results of such an approach are nevertheless limited in their statistical meaningfulness, especially since chondrocyte differentiation is merely one parameter for assessing cure-related success.